1. Field of the Invention
The invention relates to fabrics having a bright-finish metallic appearance, and more particularly to thermoplastic fabrics which are desired to have a brilliant metallic reflectance either for aesthetic reasons or for heat reflecting.
For thousands of years highly reflecting fabrics have been prized for special applications, even to the point where precious metals such as gold were incorporated in the weave. Those who could not afford such extravagance would get satin or, in modern times, synthetic fabrics which were specially treated to provide a glossy appearance. Where heat reflectance is a major consideration, aluminized fabrics have been made at great expense for protective clothing such as used for firemen or workers around furnaces, but these were not suitable for ordinary use.
In addition to fabrics used for clothing, the great interest in energy conservation over the last few years has sparked development of methods for reducing winter heat loss and summer heat gain through windows. Commercial buildings often have heat-reflecting films applied to windows, but these have not found wide application in private homes because of the nuisance in having them applied, the loss in visible light transmission which makes a slightly cloudy day seem gloomy, and the fact that the windows can have a mirror-like appearance which is always there. One solution to this dilemma is the reflecting window shade, which has a metalized film on an outside layer, and a fabric inside surface for appearance and perhaps also for insulation. However, these multi-layer shades are bulky, and tend not to hang flat because of the different characteristics of the film and the fabric.
2. Description of the Prior Art
Vapor deposition of metal onto a transparent film to produce an article suitable for gluing onto a window has been known at least since U.S. Pat. No. 3,290,203. Although the products taught therein successfully reduced heat loss, and could be tinted to provide a pleasing appearance, they could only be permanently installed (the film could be removed but not re-applied). Thus these products could not be used as a window shade, which could be rolled up as desired. More recently, metalized polyester film shades have become commercially available.
Although metalizing of film has been practiced successfully for many years, the problems involved in metalizing other materials have been solved only more slowly, and often less successfully, as pointed out in the article, "Metalizing--What it is, What it does--It's Dramatic, Efficient", published in "Paper, Film and Foil Converter", February, 1958, pp 26-29.
Up to now, the most successful commercial process for making glossy metalized fabrics has been the transfer process, by which a metal film is actually glued to fabric. This process involves preparing a transfer film by applying a "release agent" to a base or carrier film such as a polyester film. A thin film of the desired metal is then vapor-deposited on the release agent. A thin layer of adhesive is then applied over the metal layer. Another adhesive layer is applied to the fabric, and the metal layer is then transferred to the fabric by placing the adhesive-coated metal side of the film in contact with the adhesive-coated fabric, and passing them around a heated drum while holding the film against the fabric, for example by an endless blanket pulled taut around the outside of the sandwich. Although successful, this process is quite expensive, because of the cost of the carrier film, application of its multiple layers in successively different machines, and then finally the transfer process; in 1981 this procedure added more than $3.00 peryard to the cost of a fabric.
Attempts to apply metal layers to fabric directly did not produce the desired glossy appearance. Experiments with many different fabrics, including "long float" fabrics which had a glossier than average appearance before coating because of the special weave, as well as "bright yarn" fabrics of different chemical compositions, have so far been unsuccessful in producing a really high shine.